TECHNOLOGY UPDATE Glowing sensors highlight contamination
The sensor's demonstrated ability to quickly detect aflatoxins in chicken feed could make it a boon to the poultry industry, said Gregory Martin, business manager for the Poultry Science Association, a nonprofit group that includes scientists and members of the poultry industry. Aflatoxin is a known human carcinogen, and it can reduce the productivity of chickens and even kill them in high doses.
Inexpensive biosensors developed by scientists at DuPont Co. and the University of Delaware-Newark, have proven able to quickly reveal a key toxin's presence in poultry feed, as well as rapidly detecting other environmental contaminants ranging from herbicides to metals. The sensors are made by grafting genes that glow in the presence of toxic chemicals to the common E. coli bacteria. Rather than responding to the chemistry of a particular chemical, die sensors luminesce in response to DNA damage and other intracellular changes wrought by environmental stresses, explained Tina Van Dyk, research biologist at DuPont, who based her University of Delaware Ph.D. thesis on the research. Any stress activates bioluminescence in the cells including protein damage, acidification.and exposure to antibiotics, she stated, when presenting her findings at The bioluminescent bacteria on this Petri dish the March American Chemical Society glow in response to environmental toxins. meeting DuPont holds the patent on (Courtesy Amy Vollmer, Swarthmore College) fusing the glowing Photorhabdus luminescens bacteria genes to other bacThere are currently quick, inexpenteria to detect environmental stress sive, and accurate laboratory techThe technology grew out of efforts niques for detecting aflatoxin, said to screen wastewater for potentially Mamduh Sifri, poultry technical spetoxic chemicals, and Van Dyk's thesis cialist for Archer Daniels Midland, a focused on potential applications for supplier of grain to the poultry industhe poultry industry. Because the try. Van Dyk envisions that her new technology responds to general envitechnique could be used both in the ronmental stresses, it could be used to lab and as the basis for a hand-held detect any chemical in the environsensing device, although she cautions ment, she said. Testing with nine that the latter "would take a lot of dechemicals, including herbicides and velopment work." Sifri believes that metals, produced "characteristic stress both options could prove useful in the fingerprints," Van Dyk explained. poultry industry if they are accurate, inexpensive, and easy-to-use. The great sensitivity of luminescing biosensors could make sensors like Although the initial step—genetiVan Dyk's useful for applications in cally engineering the bacteria—is costly, which it is necessary to detect very once it is completed, the sensors below concentrations of chemical toxins, come inexpensive to create through said Alice Cunningham, professor the standard process of bacterial fisemerita at Agnes Scott College and the sion, Van Dyk said. All that is required author of Introduction to Bioanalytical to detect the light generated by the bacSensors. Such techniques have the "po- teria is an inexpensive photomultiplier tential for broad applicability," she said. tube, she said. —KELLYN S. BETTS © 1999 American Chemical Society
New sensor may widen monitoring capabilities A tiny new temperature sensor developed at Oak Ridge National Laboratory (ORNL) could prove valuable for chemical sensing and environmental monitoring. Eventually, the new sensor may allow the creation of wide-area monitoring networks, according to its developers. Prototype versions of the sensor, which measures 3 x 3 millimeters, use the same kind of wireless spread-spectrum technology found in advanced 900-megahertz cordless telephones. The new sensor's signal can travel 200 meters, and its circuitry is able to support four different sensory inputs. Many of the potential environmental applications would combine temperature sensing with other measurements, said Steve Smith, development engineer with ORNL's Instrumentation and Controls Division. For example, one version of the chip lists sin onboard tical detector (also developed at ORNL) that allows it to serve environmental sensor when coated with bacteria that are genetically engineered to bioluminesce in the presence of particular chemicals such as toluene Because the sensors can be networked together to allow monitoring of large areas, both EPA and the Department of Energy have expressed interest in them, Smith said. Wide-area environmental monitoring networks already are used in conjunction with the National Ambient Air Quality Standards, said Dave Musick, an environmental scientist with EPA's Office of Air and Radiation. The sensors also could prove valuable for monitoring remediation projects, Smith said. Because they are rugged, inexpensive, and relatively easy to install, they may be useful for short-term research projects, he added. —KELLYN S. BETTS
JULY 1, 1999/ENVIRONMENTAL SCIENCE & TECHNOLOGY/NEWS • 2 6 7 A
